Csc153 chapter 02

Microsoft Visual C# 2010Fourth Edition

Chapter 2Using Data

Microsoft Visual C# 2010, Fourth Edition 22

Objectives

• Learn about declaring variables

• Display variable values

• Learn about the integral data types

• Learn about floating-point data types

• Use arithmetic operators


Objectives (cont'd.)

• Learn about the bool data type

• Learn about numeric type conversion

• Learn about the char data type

• Learn about the string data type

• Define named constants and enumerations

• Accept console input

Declaring Variables

• Constant– Cannot be changed after a program is compiled

• Literal constant– Its value is taken literally at each use

• Variable– A named location in computer memory that can hold

different values at different points in time

• Data type– Describes the format and size of (amount of memory

occupied by) a data item



Declaring Variables (cont'd.)

• Variable declaration– Statement that names a variable and reserves

storage– Example: int myAge = 25;

• You can declare multiple variables of the same type – In separate statements on different lines

• You can declare two variables of the same type in a single statement– By using the type once and separating the variable

declarations with a commaMicrosoft Visual C# 2010, Fourth Edition 66

Displaying Variable Values


Displaying Variable Values (cont'd.)







• Format string– A string of characters that optionally contains fixed

text – Contains one or more format items or placeholders

for variable values

• Placeholder– Consists of a pair of curly braces containing a

number that indicates the desired variable’s position• In a list that follows the string





• Formatting outputint num1 = 4, num2 = 56, num3 = 789;

Console.WriteLine(“{0, 5}”, num1);



• Concatenate strings– Using the plus (+) sign


Using the Integral Data Types

• Integral data types– Types that store whole numbers– byte, sbyte, short, ushort, int, uint, long, ulong, and char

• Variables of type int – Store (or hold) integers, or whole numbers

• Shorter integer types– byte, sbyte (which stands for signed byte), short

(short int), or ushort (unsigned short int)


Using Floating-Point Data Types

• Floating-point number– Contains decimal positions

• Floating-point data types– float

• Can hold up to seven significant digits of accuracy

– double• Can hold 15 or 16 significant digits of accuracy

– decimal• Has a greater precision and a smaller range

• Suitable for financial and monetary calculations


Using Floating-Point Data Types (cont'd.)

• Significant digits– Specifies the mathematical accuracy of the value

• Suffixes – Put an F after a number to make it a float– Put a D after it to make it a double– Put an M after it to make it a decimal

• Scientific notation– Includes an E (for exponent)


Formatting Floating-Point Values

• C# displays floating-point numbers in the most concise way it can– While maintaining the correct value

• Standard numeric format strings– Strings of characters expressed within double

quotation marks that indicate a format for output– Take the form X0

• X is the format specifier; 0 is the precision specifier

• Format specifiers– Define the most commonly used numeric format

typesMicrosoft Visual C# 2010, Fourth Edition 1717

Formatting Floating-Point Values (cont'd.)


Using the Standard Binary Arithmetic Operators

• Binary operators– Use two values (operands)

• Operator precedence– Rules that determine the order in which parts of a

mathematical expression are evaluated– Multiplication, division, and remainder always take

place prior to addition or subtraction in an expression– You can override normal operator precedence with

parentheses


Using the Standard Binary Arithmetic Operators (cont'd.)



Using Shortcut Arithmetic Operators

• Add and assign operator– Example: bankBal += bankBal * interestRate;– Variations: –=, *=, and /=

• Prefix increment operator– Example: ++someValue;

• Postfix increment operator– Example: someValue++;

• Unary operator– Use only one value

• Decrement operator (--)

Using the bool Data Type

• Boolean variable– Can hold only one of two values—true or false– Declare a Boolean variable with type bool

• Comparison operator– Compares two items– An expression containing a comparison operator has

a Boolean value


Using the bool Data Type (cont'd.)


Understanding Numeric Type Conversion

• Arithmetic with variables or constants of the same type– Result retains the same type

• Arithmetic with operands of dissimilar types– C# chooses a unifying type for the result– Implicitly (or automatically) converts nonconforming

operands to the unifying type• Type with the higher type precedence


Understanding Numeric Type Conversion (cont'd.)

• Implicit cast– Automatic transformation that occurs when a value is

assigned to a type with higher precedence

• Explicit cast– Placing the desired result type in parentheses

• Followed by the variable or constant to be cast


Using the char Data Type

• char data type– Holds any single character

• Place constant character values within single quotation marks

• Escape sequence– Stores a pair of characters– Begins with a backslash– Pair of symbols represents a single character


Using the char Data Type (cont'd.)



Using the string Data Type

• string data type– Holds a series of characters

• Values are expressed within double quotation marks

• Comparing strings– Use == and !=– Methods Equals(), Compare(), CompareTo()


Using the string Data Type (cont'd.)





• Use the length property of a string to determine its length– The length of “water” is 5

• Use the Substring() method to extract a portion of a string from a starting point for a specific length



Defining Named Constants

• Named constant– Often simply called a constant– An identifier whose contents cannot change– Created using the keyword const

• Programmers usually name constants using all uppercase letters– Inserting underscores for readability

• Self-documenting statement– Easy to understand even without program comments



Working with Enumerations

• An enumeration is a set of constants represented by identifiers

• The following is an enumeration called DayOfWeek:enum DayOfWeek

{

SUNDAY, MONDAY, TUESDAY, WEDNESDAY

THURSDAY, FRIDAY, SATURDAY

}


Working with Enumerations (cont'd.)

• By default, enumeration values are integers– Can specify otherwise by including a colon and a

type name after the enumeration name

• The identifiers in an enumeration are often meant to hold consecutive values– When you don’t supply values, they start at 0 and

increment by 1– In the DayOfWeek enumeration, SUNDAY is 0, MONDAY is 1, and so on

Accepting Console Input

• Interactive program– A program that allows user input

• Console.ReadLine() method– Accepts user input from the keyboard– Accepts all of the characters entered by a user until

the user presses Enter– Characters can be assigned to a string– Must use a conversion method to convert the input

string to the proper type


Accepting Console Input (cont'd.)


Accepting Console Input (cont'd.)


You Do It

• Activities to explore– Declaring and Using variables– Performing Arithmetic– Working with Boolean Variables– Using Escape Sequences– Writing a Program that Accepts User Input


Summary

• Constant: cannot be changed after compilation

• Can display variable values with Write() or WriteLine()

• Nine integral data types: byte, sbyte, short, ushort, int, uint, long, ulong, and char

• Three floating-point data types: float, double, and decimal

• Use the binary arithmetic operators +, –, *, /, and % to manipulate values in your programs

• Shortcut arithmetic operators



Summary (cont'd.)

• A bool variable can be true or false

• Implicit cast versus explicit cast• char data type holds any single character• string data type holds a series of characters

• Named constants are program identifiers whose values cannot change.

• Console.ReadLine() method accepts user input

Csc153 chapter 02

Technology

exponentmicrosoft visual

signmicrosoft visual

parenthesesmicrosoft

commamicrosoft visual

stringmicrosoft visual

data itemmicrosoft visual

variable values contd

string data type